It is proposed to carry out calculations, using both the FN method (lately extended to three-dimensional radiation transport by the proposers) and the Monte Carlo technique, of near-infra-red (IR) transmission through plane-parallel slabs exposed to pencil beams (diameter is dominated by 1 mm). The calculations are expected to give extensive information on penetration and scattering as a function of wavelength, including the radial and angular distributions of the emergent flux. A limited experimental program will check the calculations where input data is available and will seek to provide basic attenuation information, etc., where such data is lacking as a starting point for computation. The objective of the study is to examine the feasibility of applying the well-known "flying-spot" principle, which rejects image-degrading scattered radiation, to transmitted-IR imaging of thin body parts such as the female breast. Such examinations now rely on wide (and thus scatter-rich) beams of visible light. The advantages of such a scanner in spite of its poor spatial resolution are expected to include (1) improved contrast because of scatter rejection, (2) sensitivity to certain chemical as well as physical properties of tissues, (3) effectively real-time output with no IR film processing, (4) availability of digital output, facilitating, e.g., contrast enhancement, multi-wavelength techniques, etc., (5) daylight operation, (6) complete absence of risk, so far as is known, except for an easily-managed ophthalmological hazard, and (7) modest cost, portability and elimination of special examination rooms. Items (6) and (7) would facilitate use in mass screening. The present project is likely to provide feasibility and design information on a device whose clinical and commercial possibilities are considerable, without the expense and risk of a full developmental study. Phase II and/or other funding will be sought if feasibility is established in Phase I.